1. Field of the Invention
The present invention relates to an object, a method, a manufacturing method, a process, a machine, manufacture, or a composition of matter. In particular, one embodiment of the present invention relates to a semiconductor device, a display device, a light-emitting device, a driving method thereof, or a manufacturing method thereof.
In this specification, a semiconductor device generally means a device which can function by utilizing semiconductor characteristics. Electro-optical devices, display devices, memory devices, semiconductor circuits, and electronic devices are in some cases included in semiconductor devices and in other cases include semiconductor devices.
2. Description of the Related Art
Attention has been focused on a technique for forming a transistor using a semiconductor layer (also referred to as a thin film transistor (TFT)). The transistor is applied to a wide range of electronic devices such as an integrated circuit (IC) or an image display device (display device). A silicon-based semiconductor layer is widely known as a semiconductor layer applicable to such a transistor. As another material, an oxide semiconductor layer is attracting attention.
For example, a transistor including an amorphous oxide semiconductor layer containing indium (In), gallium (Ga), and zinc (Zn) in a channel formation region is disclosed (see Patent Document 1).
In a transistor including an oxide semiconductor layer serving as a channel formation region, an oxygen vacancy (also referred to as an oxygen defect) is generated by release of oxygen from the oxide semiconductor layer, and a carrier is generated owing to the oxygen vacancy. It is known that, to solve the above problem, oxygen released from a silicon oxide film containing excess oxygen is supplied to the oxide semiconductor layer to fill the oxygen vacancy in the oxide semiconductor layer, whereby a highly reliable semiconductor device with small change in electrical characteristics can be provided (see Patent Document 2).